The ehrlichiae are obligate intracellular bacteria that infect circulating leucocytes. Ehrlichia chaffeensis infects the monocytes and macrophages in humans and causes human monocytic ehrlichiosis. The clinical manifestations of ehrlichiosis in humans are nonspecific and similar to Rocky Mountain spotted fever. The clinical manifestations include fever, chills, headache, myalgia or vomiting, and weight loss. Most patients have a history of tick exposure.
Ehrlichia canis infects and causes ehrlichiosis in animals belonging to the family Canidae. Canine ehrlichiosis consists of an acute and a chronic phase. The acute phase is characterized by fever, serous nasal and ocular discharges, anorexia, depression, and loss of weight. The chronic phase is characterized by severe pancytopenia, epistaxis, hematuria, blood in feces in addition to more severe clinical signs of the acute disease. If treated early during the course of the disease, dogs respond well to doxycycline. However, chronically infected dogs do not respond well to the antibiotic. Therefore, early diagnosis is very important for treating canine ehrlichiosis.
The primary diagnostic test for diagnosing canine ehrlichiosis and human ehrlichiosis is the indirect fluorescent antibody (IFA) test. This test uses the etiologic agent Ehrlichia canis to diagnose canine ehrlichiosis. The IFA test uses Ehrlichia chaffeensis as antigen for diagnosing human ehrlichiosis. The IFA test has, however, serious limitations. The IFA test is subject to false positives because the antigens are made of whole infected cells which comprise many nonspecific proteins which will cross-react with sera from some patients. The IFA test is also subject to false negatives because IFA antigens are unstable and may become inactivated during storage. In addition the IFA test requires a special equipment to perform the test. For example, the IFA test requires a tissue culture system for growing the bacterium that are used to prepare the antigen slides, a fluorescent microscope, and trained persons to evaluate the serum reactivity to the bacterial antigen on the slide.
Tools which permit simpler, more rapid, and objective serodiagnosis of canine ehrlichiosis or human ehrlichiosis are desirable.
The present invention relates to improved diagnostic tools for veterinary and human use which are used for serodiagnosing ehrlichiosis in mammals, particularly in members of the Canidae family and in humans. The diagnostic tools are a group of outer membrane proteins of E. chaffeensis and variants thereof, referred to hereinafter as the xe2x80x9cOMP proteinsxe2x80x9d, a group of outer membrane proteins of E. canis and variants thereof referred to hereinafter as the xe2x80x9cP30F proteinsxe2x80x9d, and antibodies to the OMP proteins and the P30F proteins.
The OMP proteins of E. chaffeensis encompass OMP-1, OMP-1A, OMP1-B, OMP-1C, OMP1-D, OMP1-E, OMP1-F, OMP1-H, OMP-1R, OMP-1S, OMP-1T, OMP-1U, OMP-1V, OMP-1W, OMP-1X, OMP-1Y and OMP-1Z. The mature OMP-1 protein of E. chaffeensis has a molecular weight of about 27.7 kDa and comprises amino acid 26 through amino acid 281 of the sequence shown in FIG. 3B, SEQ ID NO: 2. The mature OMP-1B protein of E. chaffeensis has a molecular weight of about 28.2 kDa and comprises amino acid 26 through amino acid 283 of the sequence shown in FIG. 4B, SEQ ID NO: 4. The mature OMP-1C protein of E. chaffeensis has a molecular weight of about 27.6 kDa and comprises amino acid 26 through amino acid 280 of the sequence shown in FIG. 5B, SEQ ID NO: 6. The mature OMP-1D protein of E. chaffeensis has a molecular weight of about 28.7 and comprises amino acid 26 through amino acid 286 of the sequence shown in FIG. 6B, SEQ ID NO: 8. The mature OMP-1E protein of E. chaffeensis has a molecular weight of about 27.8 kDa and comprises amino acid 26 through amino acid 278 of the sequence shown in FIG. 7B, SEQ ID NO: 10. The mature OMP-1F protein of E. chaffeensis has a molecular weight of about 27.9 kDa and comprises amino acid 26 through amino acid 280 of the sequence shown in FIG. 8B, SEQ ID NO: 12. The mature OMP-1A protein of E. chaffeensis has a molecular weight of about 29.6 kDa and comprises amino acid 31 through amino acid 297 of the sequence shown in FIG. 9B, SEQ ID NO: 14. The mature OMP-1R protein of E. chaffeensis has a molecular weight of about 19.7 kDa and comprises amino acid 29 through amino acid 196 of the sequence shown in FIG. 10B, SEQ ID NO: 16. The mature OMP-1S protein of E. chaffeensis has a molecular weight of about 29.2 kDa and comprises amino acid 26 through amino acid 291 of the sequence shown in FIG. 11B. SEQ ID NO: 18. The OMP-1T protein of E. chaffeensis comprises the amino acid sequence shown in FIG. 12B, SEQ ID NO: 20. The mature OMP-1U protein of E. chaffeensis has a molecular weight of about 30.6 kDa and comprises amino acid 26 through amino acid 295 of the sequence shown in FIG. 13B, SEQ ID NO: 22. The mature OMP-1V protein of E. chaffeensis has a molecular weight of about 28.0 kD and comprises amino acid 27 through amino acid 279 shown in FIG. 14B, SEQ ID NO: 24. The mature OMP-1W protein of E. chaffeensis has a molecular weight of about 28.8 kDa and comprises amino acid 30 through amino acid 283 of the sequence shown in FIG. 15B, SEQ ID NO: 26. The mature OMP-1X protein of E. chaffeensis has a molecular weight of about 27.8 kDa and comprises amino acid 25 through amino acid 275 of the sequence shown in FIG. 16B, SEQ ID NO: 28. The mature OMP-1Y protein of E. chaffeensis has a molecular weight about 28.8 kDa and comprises amino acid 28 through amino acid 285 of the sequence shown in FIG. 17B, SEQ ID NO: 30. The mature OMP-1Z protein of E. chaffeensis has a molecular weight of about 30.2 kDa and comprises amino acid 27 through amino acid 300 of the sequence shown in FIG. 18B, SEQ ID NO: 50. The mature OMP-1H protein has a molecular weight of about 30.2 kDa and comprises the amino acid 27 through amino acid 298 of sequence shown in FIG. 33B, SEQ ID NO: 52.
The outer membrane proteins from E. chaffeensis, particularly a recombinant form of OMP-1, are immunogenic and, thus are useful for preparing antibodies. Such antibodies are useful for immunolabeling isolates of E. chaffeensis and for detecting the presence of E. chaffeensis in body fluids, tissues, and particularly in monocytes and macrophages. The OMP proteins, particularly OMP-1, are also useful for detecting antibodies to E. chaffeensis in the blood of patients with clinical signs of ehrlichiosis. The OMP protein, particularly OMP-1, are also useful immunogens for raising antibodies that are capable of reducing the level of infection in an immunized mammal that has been infected. with E. chaffeensis. The proteins are also useful in a vaccine for protecting against infection with E. chaffeensis. 
The P30F proteins of E. canis encompass P30, P30a, P30-1, P30-2, P30-3, P30-4, P30-5, P30-6, P30-7, P30-8, P30-9, P30-10, P30-11, and P30-12. The mature P30 protein of E. canis has a molecular weight of about 28.8 kDa and comprises amino acid 26 through amino acid 288 of the sequence shown in FIG. 19B, SEQ ID NO: 32. The mature P30a protein of E. canis has a molecular weight of about 29.0 kDa and comprises amino acid 26 through amino acid 287 of the sequence shown in FIG. 20B, SEQ ID NO: 34. The mature P30-1 protein of E. canis has a molecular weight of about 27.7 kDa and comprises amino acid 55 through amino acid 307 of the sequence shown in FIG. 21B, SEQ ID NO: 36. The mature P30-2 protein of E. canis has a molecular weight of about 28.0 kDa and comprises amino acid 26 through amino acid 280 of the sequence shown in FIG. 22B, SEQ ID NO: 38. The mature P30-3 protein of E. canis has a molecular weight of about 28.7 kDa and comprises amino acid 26 through amino acid 283 of the sequence shown in FIG. 23B, SEQ ID NO: 40. The mature P30-4 protein of E. canis has a molecular weight of about 28.0 kDa and comprises amino acid 26 through amino acid 276 of the sequence shown in FIG. 24B, SEQ ID NO: 42. The mature P30-5 protein of E. canis has a molecular weight of about 29.4 kDa and comprises amino acid 27 through amino acid 293 of the sequence shown in FIG. 25B, SEQ ID NO: 44. The mature P30-6 protein of E. canis has a molecular weight of about 29.4 kDa and comprises aminoacid 31 through amino acid 293 of the sequence shown in FIG. 26B, SEQ ID NO: 54. The mature P30-7 protein of E. canis has a molecular weight of about 29.9 kDa and comprises amino acid 31 through amino acid 296 of the sequence shown in FIG. 27B, SEQ ID NO: 56. The mature P30-8 protein of E. canis has a molecular weight of about 30.3 kDa and comprises amino acid 27 through amino acid 299 of the sequence shown in FIG. 28 B, SEQ ID NO: 46. The mature P30-9 protein of E. canis has a molecular weight of about 28.6 kDa and comprises amino acid 27 through amino acid 281 of the sequence shown in FIG. 29B, SEQ ID NO: 58. The mature P30-10 protein of E. canis has a molecular weight of about 28.1 kDa and comprises amino acid 26 through amino acid 280 of the sequence shown in FIG. 30B, SEQ ID NO: 48. The mature P30-11 protein of E. canis has a molecular weight of about 28.6 kDa and comprises the amino acid 26 through amino acid 279 of sequence shown in FIG. 31B, SEQ ID NO: 60. The P30-12 protein of E. canis has a molecular weight of at least 27.3 kDa and comprises the amino acid sequence shown in FIG. 32B, SEQ ID NO: 62.
The P30F proteins, particularly P30, are immunogenic and are, thus, useful for preparing antibodies that are useful for immunolabeling isolates of E. canis. The P30 protein is also useful for diagnosing canine ehrlichiosis in mammals, particularly in members of the family Canidae, most particularly in dogs and for diagnosing infections with E. chaffeensis in humans. The P30F proteins are also useful immunogens for raising antibodies that reduce the level of infection in an immunized mammal that has been infected with E. canis. The P30F protein are also useful in a vaccine for protecting animals against infection with E. canis. 
The present invention also provides isolated polynucleotides that encode the E. chaffeensis OMP proteins and isolated polynucleotides that encode the E. canis P30F proteins. The present invention also relates to antibodies which are immunospecific for and bind to the OMP proteins and the P30F proteins. Such antibodies are useful for immunolabeling isolates of E. chaffeensis and E. canis. The present invention also relates to kits containing reagents for diagnosing human ehrlichiosis and canine ehrlichiosis and to immunogenic compositions containing one or more OMP proteins or P30F proteins.